For instance, heretofore, Patent Document 1 listed below discloses a technique to form a cage-shaped distributed winding coil in such a manner that a plurality of wave winding coils each made of a flat conductor wire wound in a wave form are prepared and those coils are arranged to overlap with displacement of pitches from one another. However, the technique disclosed in Patent Document 1 could not achieve a cage-shaped distributed winding coil by simply overlapping the wave winding coils. This needs a step of sequentially braiding the wave winding coils. Coil production efficiency is therefore low.
The present applicants therefore propose, in Japanese patent application No. 2009-16549, a cage-shaped distributed winding coil that does not need the step of sequentially braiding the wave winding coils and thus can enhance the production efficiency. A flat conductor wire (“flat wire”) constituting this cage-shaped distributed winding coil has a rectangular cross-section and is formed continuously in a meandering (rectangular-waves) pattern. This flat raw wire includes in-slot wire portions to be arranged to overlap one another in each slot of a stator core so that a long side of the rectangular cross-section is directed along a diameter direction of the stator core, circumferential conductor portions (coil-end portions) to be arranged to overlap one another at coil ends so that a short side of the rectangular cross-section is directed along to the diameter direction of the stator core, and bent portions (including twisting raw portions) bent to join the in-slot wire portions and the coil-end wire portions. Further, the above flat wires are overlapped to be wound by multiple turns, so that the in-slot wire portions and the coil-end wire portions are respectively overlapped one another, forming a cage-shaped distributed winding coil. This cage-shaped distributed winding coil is installed in a stator core by inserting the in-slot wire portions in the slots. In this way, a stator is obtained.